94 SHIPPING PRACTICE
In this column full particulars are given of the engines
and boilers. For the purpose of this volume it is only
necessary to draw attention to the notations "C," "T," and
"0" which classify the engines into "compound/* "triple,"
or "quadruple" expansion engines in the case of steamers.
The notations "Oil Engines," "Turbines," "Steam tur-
bines connected to Electric Motors and Screwshafts"
(Turbo-electric), "Oil Engines connected to Electric Motors
and Screwshafts" (Diesel-electric) and "Steam turbines
SR geared to 2 sc. shafts" are self-explanatory.
The record "Spt" immediately after the number and
description of the main boilers, e.g. "sSB Spt," indicates
that the main boilers are equipped with superheaters.
The letters "OF" denote that a ship's boilers are fitted
for burning oil fuel, but does not imply that they are actu-
ally running on such fuel. In the case of classed vessels
a note of the date of fitting the oil-burning installation is
Other abbreviations which can appear in this and other
columns, but which are not specifically mentioned in these
notes, are clearly explained in the Key to the Register.
As regards the principal periodical surveys required for
class maintenance, in addition to the four-yearly Special
Surveys already referred to (the requirements for which
become progressively more severe as the ship's age increases)
the boilers and/or donkey boilers of a ship are required to
be submitted to annual survey by the Society's surveyors,
but in the case of "Scotch" (e.i. non-watertube) boilers this
is not required until six years have elapsed from the date of
build. (N.B. The boilers, together with the main and
auxiliary machinery, are examined as part of every four-
yearly Special Survey unless seen within the preceding
twelve months.) Screwshafts fitted with continuous liners
or with oil glands become due for survey at intervals of
three years (four years in the case of ships fitted with two
or more screwshafts). Shafts not fitted with these appliances
are required to be surveyed every two years. A survey of